ABSTRACT
When concrete elements are used to support loads, various stresses are introduced into the concretemainly tensile, compressive and shear stresses. These stresses are countered by the strength of the concrete and the steel reinforcement, which provide the necessary resistance to enable the element to sustain the design loads and forces. As deflection under load takes place, steel elongates and the concrete in the bottom of the beam cracks. The deflection and cracking are determined by the designer within acceptable limits and the elements can be used economically during the lifetime of the building or structure. As spans between supports or the loads to be carried increase, so the section of the reinforced concrete must be increased or their spacing within the structure must be decreased. Greater volumes of concrete must be used, the additional mass of which further increases the stresses within the elements.
